Purpose: We aimed to describe the use of high-flow nasal oxygen (HFNO) in patients with COVID-19 acute
respiratory failure and factors associated with a shift to invasive mechanical ventilation.
Methods: This is a multicenter, observational study from a prospectively collected database of consecutive COVID-
19 patients admitted to 36 Spanish and Andorran intensive care units (ICUs) who received HFNO on ICU admission
during a 22-week period (March 12-August 13, 2020). Outcomes of interest were factors on the day of ICU
admission associated with the need for endotracheal intubation. We used multivariable logistic regression and
mixed effects models. A predictive model for endotracheal intubation in patients treated with HFNO was derived
and internally validated.
Results: From a total of 259 patients initially treated with HFNO, 140 patients (54%) required invasive mechanical
ventilation. Baseline non-respiratory Sequential Organ Failure Assessment (SOFA) score [odds ratio (OR) 1.78; 95%
confidence interval (CI) 1.41-2.35], and the ROX index calculated as the ratio of partial pressure of arterial oxygen to
inspired oxygen fraction divided by respiratory rate (OR 0.53; 95% CI: 0.37-0.72), and pH (OR 0.47; 95% CI: 0.24-0.86)
were associated with intubation. Hospital site explained 1% of the variability in the likelihood of intubation after
initial treatment with HFNO. A predictive model including non-respiratory SOFA score and the ROX index showed
excellent performance (AUC 0.88, 95% CI 0.80-0.96).
Conclusions: Among adult critically ill patients with COVID-19 initially treated with HFNO, the SOFA score and the
ROX index may help to identify patients with higher likelihood of intubation
